The ball valve described in German Utility Patent 87 00 106 has a valve seat made from identical sintered ceramic seat rings.
The combination of a sintered ceramic valve seat and a sintered ceramic valve ball is characterized by high wear resistance with good resistance to erosion, abrasion and cavitation as well as a good corrosion resistance. However the pressure seal of the valve is unsatisfactory.
Experience shows that a gastight valve of this specific type with a sintered ceramic valve seat and a sintered ceramic valve ball cannot be made and/or is not practical.
On the other hand a ball valve in a different form is known in practice in which the seat rings comprise flexible, especially elastically deformable material. Also here the valve seat comprises identically formed seat rings. However the known ball valve with a valve seat formed from an elastomer has an insufficiently long service life, especially in abrasive media and with overcritical expansion of the conveyed fluid.